The present invention relates to a machine translation system for processing an original sentence to obtain a translated sentence and, more particularly, to a machine translation system which can improve translation efficiency and can obtain a more natural-sounding translated sentence.
In recent years, various machine translation systems which perform translation by using a computer, e.g., a processing system for translating English sentences into Japanese sentences or a processing system for translating Japanese sentences into English sentences, have been developed.
Basic processing in a conventional machine translation system will be briefly described.
(1) Morphological, syntactic, and semantic analyses are performed for a given original sentence, and the original sentence is divided into predetermined processing units, e.g., words (or phrases). PA1 (2) A dictionary (translation dictionary) as a data base of language information necessary for translation processing is searched to obtain translated words (or translated phrases) in the processing units of the original sentence. PA1 (3) These translated words (translated phrases) are connected according to predetermined syntactic rules for translated sentence generation, thus generating a translated sentence of the original sentence.
However, a technique for interpreting verbal meanings in a natural language has not yet been established. For this reason, it is difficult to immediately obtain an appropriate translated sentence through the above-mentioned machine translation. Furthermore, since there are an infinite number of sentences that can be expressed with words and phases in the original language, it is not always possible for machines to generate appropriately natural-sounding translated sentences of all of these original sentences.
In the conventional machine translation system, a translated sentence is provided with punctuation marks in correspondence with punctuation marks present in an original sentence in order to obtain a sentence which is at least easy to read. More specifically, the punctuation marks in the original sentence are directly transferred to the corresponding punctuation marks or words, and are arranged at positions in the translated sentence corresponding to those in the original sentence. (When translated sentences have no punctuation marks corresponding to those in an original sentence, the punctuation marks in the original sentence are often replaced with proper words corresponding to the meanings of the punctuation marks in the original sentence in some languages.)
However, if original and translated sentences are different from each other in terms of their syntactic structures, it is often difficult to determine positions of punctuation marks in a translated sentence corresponding to the punctuation marks in an original sentence. Some languages are expressed with almost no punctuation marks, and some are difficult to understand unless many punctuation marks are used.
Even if a translated sentence is simply marked off by punctuation marks in correspondence with those in an original sentence, a natural-sounding translated sentence which is easy to read cannot often be obtained.